In recent years, downsized mobile devices have spread worldwide, and simultaneously, the demand for downsized large-capacity nonvolatile memory has rapidly increased with the drastic progress of high-speed telecommunications networks. Therein, NAND flash memory and downsized HDDs (hard disk drives) in particular have achieved rapid advancements of recording density to form a large market.
Under such circumstances, several ideas for new memory aiming to drastically exceed the limits of recording density have been proposed.
These include a memory using a resistance change material having a low resistance state and a high resistance state. The characteristics of the low resistance state and the high resistance state may fluctuate when repeatedly causing such a resistance change material to transition between the low resistance state and the high resistance state. Therefore, it is desirable to increase the repeated-operational stability.
JP-A 2007-288016 (Kokai) discusses technology in which a changeable resistance film is interposed between a lower metal electrode and an upper metal electrode; the changeable resistance film is doped with atoms included in the lower metal electrode and the upper metal electrode; and it is attempted to simplify a process called forming.
On the other hand, United States Patent Application Publication No. 2007/0240995 A1 discusses a configuration in which the resistance change layer includes Fe2O3 and Fe3O4; and the lower electrode has a composition which is different from that of the resistance change layer and is made of iron oxide including Fe3O4.